Match three before the maw is fed
The line rolls on whether you are ready or not. Put a marble into it so that three of one colour touch and they shatter, and the line is that much shorter.
A match splits the line, and the tail runs forward to close the gap. If the colours meet, they go too — and each link is worth more than the last. Ten deep is possible.
Some carry a charge that blows a hole in the line, a clock that slows everything down, an arrow that runs the whole track backwards, or a sight that draws your line for you.
A long cut, a tight coil, two gates feeding two maws at once, and an overpass that brings the line in over your head. Clear the eighth and the quarry starts again, faster.
Every marble is a lit sphere that rotates by exactly as far as it has travelled, in a channel cut through the quarry floor. Six colours, six surfaces, no two alike.
The run saves itself as you play, so closing the tab costs you nothing. Behind it sits a lifetime record: shots fired, accuracy, longest cascade and your ten best runs.